1. Field of the Invention
This invention relates to new, dual promoted, high surface area, iron/manganese spinel compositions promoted with copper and with a Group IA or Group IIA metal, their preparation and use. More particularly, this invention relates to new, unsupported, single phase Fe-Mn spinel compositions dual promoted with copper and a Group IA or Group IIA metal, their preparation and use as catalysts in FischerTropsch slurry processes for producing alpha olefins from mixtures of CO and H.sub.2. These catalysts have a surface area greater than about 30 M.sup.2 /g in which the atomic ratio of Fe to Mn is greater than 2:1.
2. Background of the Disclosure
Fischer-Tropsch processes have long been known to produce gaseous and liquid hydrocarbons containing C.sub.2 -C.sub.4 olefins. Because of the importance of C.sub.2 -C.sub.4 olefins, particularly as feedstocks for the chemical industry, modifications of the Fischer-Tropsch process are constantly being pursued toward the goals of maximizing C.sub.2 -C.sub.4 olefin selectivity with the particular objective of maintaining high catalyst activity and stability under the reaction conditions. The main thrust of the efforts in this area has been in the area of catalyst formulation.
Coprecipitated and/or supported iron-based catalysts, including those containing manganese, are known for producing C.sub.2 -C.sub.4 olefins. Examples of disclosures in the art directed to such iron-manganese catalysts and/or alloys include: W. L. vanDijk, et al., Appl. Catal., 2,273 (1982); Eur. Pat. Appl. 49888 to Ruhrchemie (1981); H. J. Lehman, 73rd AIChe Meeting Paper #103D; W. D. Deckwer, et al., Chem. Ing. Tech., 53 (10), 818 (1981); V. Rao and R. Gormley, Hydrocarbon Processing, 139, November (1981); H. Kolbel and K. Tillmetz, U.S. Pat. No. 4,177,203 (1970); EPO Patent Publication 0,071,770; U.S. Pat. No. 2,605,275; U.S. Pat. No. 2,850,515; Prepr. Div. Pet. Chem. Am. Chem. Soc. (1978) 23(2) pp 513-20; Intersoc. Energy Convers. Eng. Conf. 1978, 13(1) pp 482-6; U.S. Pat. No. 4,186,112; EP 49,888; React. Kinet. Catal. Lett. 1982, 20(1-2) pp 175-80; U.S. Pat. No. 2,778,845; Khim (1) Tekhnol. Topliv i Masel (Russ.) 10(6) 5-10 (1965); UK Patent Appln. 2,050,859 A; German Patent Appln. DT 2919-921; Prace Ustavu Vyzkum Paliv 8, p. 39-81 (1964) (Czech).
An iron-manganese spinel of the formula, Fe.sub.2 MnO.sub.4, is reported as a catalyst component formed during Fischer-Tropsch synthesis in which a coprecipitated Fe/Mn oxide catalyst is initially employed in Applied Catalysis 5 (1983) pp. 151-170.
U.S. Pat. No. 2,778,845 to McGrath, et al. discloses a non-spinel type, low surface area, sintered catalyst composition containing reduced or metallic iron as a major component. These compositions are used to synthesize hydrocarbons from mixtures of hydrogen and and carbon monoxide and are formed via a high temperature fusion in an electric arc furnace. The preferably in hydrogen, to form the metallic iron-containing catalyst. U.S. Pat. No. 2,605,275 to Kearby, et. al. discloses forming hydrocarbons from mixtures of CO and H.sub.2 employing low surface area, sintered, spinel type catalysts containing iron and a divalent metal of the general formula Fe.sub.2 MeO.sub.4 wherein Me is the divalent metal. The molar ratio of Me to Fe.sub.2 O.sub.3 is preferably greater than 1:1. Thus, the ratio of Fe/Me is no greater than 2/1 and preferably less than 2/1.
U.S. Pat. No. 3,970,738 to Matsui, et al. discloses an iron oxide composition containing a minor amount of manganese oxide and a process for making same. The object of the invention in this disclosure is stated as being able to provide iron oxide products substantially free from manganese compounds as impurities. The upper limit on the manganese component of these iron oxide products is taught and claimed as being less than 0.2 weight percent calculated as MnO. Maiti, et al. in "Iron/Manganese Oxide Catalysts for Fischer-Tropsch Synthesis. Part I: Structural and Textural Changes By Calcination, Reduction and Synthesis", J. Applied Catalysis, v5, p. 151-170 (1983) discloses the use of iron-manganese containing catalysts in a Fischer-Tropsch process to produce olefins. Spinel compositions are suggested as being present in the catalysts used in this reference. This reference does not disclose the use of copper and potassium promoted spinels.
Van Dijk, et al. in "Effects of Manganese Oxide and Sulfate on the Olefin Selectivity of Iron Catalysts in the Fischer Tropsch Reaction", J. Applied Catalysis, v2, p. 273-288 (1982) disclose a Fischer-Tropsch catalyst which, on page 277, is set forth as a mixture of alpha iron oxide, alpha iron hydroxide and Mn.sub.2 O.sub.3. This reference discloses that these catalysts produce substantially more than about 20% methane make and an equilibrium methane selectivity (on page 283) of over 30%. U.S. Pat. No. 4,177,203 to Kolbel, et al. discloses, in line 6-9 of column 3, a Fischer-Tropsch process using a catalyst which contains more than 50% manganese and less than 50% iron. This process produces low molecular weight olefins. Kolbel, et. al. in "Feedstock For Chemical Industry By Selective Fischer-Tropsch-Synthese", 1978 Society of Automotive Engineers, p. 482-486, disclose a Fischer-Tropsch catalyst consisting of a precipitated mixture of gamma Mn.sub.2 O.sub.3 and alpha Fe.sub.2 O.sub.3 inserted in the manganese oxide lattice. Thus, the catalyst composition of this reference consists of mixed oxide phases. Further, the ratio of manganese to iron oxide of the catalyst disclosed therein is set forth as being between 8 and 10.
European Patent No. 71,770 discloses iron-manganese catalysts promoted with potassium, wherein the maximum ratio of iron to manganese is 1:2. Compositions set forth in the Tables on pages 11 and 13 of this reference disclose iron/manganese ratios of 1:3.
Bruce, et al. in "Light Olefin Production From CO/H.sub.2 Over Silica Supported Fe/Mn/K Catalysts Derived From a Bimetallic Carbonyl Anion, [Fe.sub.2 Mn(CO).sub.12 ]", React. Kinet. Catal. Lett., v. 20, Nos. 1-2, p. 175-180 (1982) disclose olefin production using supported catalysts prepared from carbonyl precursors, with silica being the support. Methane selectivity incurred with the use of this catalyst in Fischer-Tropsch hydrocarbon synthesis reactions is disclosed as about 31% (unpromoted) and 18% (potassium promoted).
Jenson, et al. in "Studies on Iron-Manganese Oxide Carbon Monoxide Catalysts; I. Structure of Reduced Catalyst", J. of Catalysts, v. 92, p. 98-108 (1985) disclose iron-manganese catalysts showing enhanced selectivity for low molecular weight olefins from synthesis gas. The reduced catalyst composition is disclosed as having been found to be an alpha iron oxide and a manganese (II oxide) as separate phases, with the manganese oxide phase containing some divalent iron oxide in solid solution. Maiti, et al. in "Iron/Manganese Oxide Catalysts For Fischer-Tropsch Synthesis. Part II, Crystal Phase Composition, Activity and Selectivity" J. Appl. Catal. 16 (2) 215-25 (1985) disclose structural changes in the Fe--Mn oxide system under synthesis gases as a function of various pretreatments.
French Patent No. 2,554,433 discloses passing a mixture of H.sub.2 and CO over a spinel catalyst having the general formula of Li.sub.x Cu.sub.1-x Fe.sub.5 O.sub.8 and French Patent No. 2,553,399 discloses a similar process employing a catalyst having the general formula of Cu.sub.x Mn.sub.1-x Fe.sub.y Cr.sub.1 -yO.sub.4.
Finally, Pennline, et al. in "The Effect of Activation and Promotion on a Fischer-Tropsch Catalyst" 189th ACS National Meeting (Miami Beach 4/28-5/3/85) ACS Div. Fuel Chem. Prep. 30# 2:310-17 (1985) disclose a Fischer-Tropsch catalyst employed in a slurry reactor employing catalysts containing 21% iron 79% manganese oxide activated in-situ, under various conditions.
However, none of the references cited above describe a Fischer-Tropsch hydrocarbon process employing an unsupported single phase Fe/Mn spinel catalyst having an Fe:Mn atomic ratio above 2:1 and a surface area greater than about 30 M.sup.2 /g and being dual promoted with both copper and a Group IA or IIA metal promoter agent.